Stool Color Changes

Benjamin Wedro, MD, FACEP, FAAEM

Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

Black
tarry stools or
blood in the stool
should never be ignored and can be a medical emergency if the cause is
bleeding from the stomach, small intestine or colon.

The health-care professional may want to
observe the color of the stool to help with the diagnosis. Sometimes a rectal
examination is performed and that stool can be evaluated and tested. Sometimes,
the patient needs to bring a stool sample from home to be inspected.

The treatment for stool color changes is
directed at the underlying illness.

Definition of stool color changes

Stool, feces, or poop is the waste product of digestion. Food mixes with bile from the liver and digestive enzymes from the pancreas allowing protein, carbohydrates, and fats in the diet to be broken down to form a slurry. This liquid mixture passes through the small intestine where nutrients are absorbed into the blood stream and the leftover liquid waste is delivered to the colon. In the colon, water is absorbed and results in stool formation. Normal stool contains bacteria, digested food, cellulose from undigested plant material, and bile. The quality, quantity, and color of stool is an indicator of gastrointestinal health and changes may be significant.

What is the color of normal stool?

Stool (feces) color is most commonly brown. When stool color changes, often, an individual becomes concerned. The presence of the bilirubin (a breakdown product of blood) in bile is generally responsible for stool color. Bilirubin concentration can vary the color of bile color from light yellow to almost black in color. Changes in bilirubin can cause stool to turn green, gray, or clay-like in color. Intestinal bleeding may turn stool black, tarry, red, maroon, or smelly stool. Medication and food may also affect stool color.

Most stool-to-stool changes in color have little meaning. However, some changes, particularly if the changes are consistent over time and not present in only one stool, can be important.

What are the causes of stool color changes?

Stool color changes are not symptoms of disease in most cases. Changes in stool color may be due to:

Diarrhea may produce green stools caused by a number of reasons.

Abdominal pain may produce clay-colored stools.

Back pain may signal a tumor blocking the bile ducts.

Upper or lower abdominal pain (sometimes caused by bleeding in the GI tract).

Nausea and vomiting associated with stool color changes may be from heavy associated bleeding.

Rectal Bleeding (Blood in Stool, Hematochezia)

Causes of Blood in Stool

Blood in the stool can be bright red, maroon in color, black and tarry, or occult (not visible to the naked eye). Causes of blood in stool range from harmless, annoying conditions of the gastrointestinal tract such as hemorrhoids to serious conditions such as cancer.